UNDERSTANDING ANESTHESIA

1. UNDERSTANDING ANESTHESIA

2. Objectives • Identify the different types of anesthesia management • Identify common anesthetic agents & their influence on patient subsystems • Identify the stages of general anesthesia • Discuss appropriate actions in the event of a malignant hyperthermia crisis

3. Anesthesia • The word is derived from the Greek words an, which means “without” and aithesia which means “feeling” • The use of medical anesthesia was first reported in 1846 • The development of anesthesia has made today’s modern surgical techniques possible

4. ASA Physical Status Classification • ASA 1 – normal, healthy patient • ASA 2 – patient with mild, well-controlled systemic disease • ASA 3 – patient with severe systemic disease that limits activity • ASA 4 –patient with severe, life-threatening disease • ASA 5 – moribund patient not expected to survive for 24 hours with or without surgery An “E” is added to the classification for emergent procedures

5. General Anesthesia • Effects of general anesthesia: • Effects are produced by depression of the CNS & blocking pain stimuli at the level of the cerebral cortex • Hypnosis (sleep) • Analgesia • Amnesia • Muscle relaxation

6. General Anesthesia • Anesthesia is generally induced by a combination of drugs: • inhalation & intravenous anesthetics • intravenous narcotics & sedatives • muscle relaxants

7. Complications Associated with General Anesthesia • Laryngospasm • Nausea & Vomiting • Damage to teeth during intubation • Corneal abrasions • Aspiration • Malignant hyperthermia

8. Regional Anesthesia • Defined as “a reversible loss of sensation in a specific area of the body” • Spinal anesthesia • Epidural anesthesia • IV Regional Blocks • Peripheral Nerve Blocks

9. Spinal Anesthesia • A local anesthetic agent (lidocaine, tetracaine or bupivacaine) is injected into the subarachnoid space • Spinal anesthesia is also known as a subarachnoid block • Blocks sensory and motor nerves, producing loss of sensation and temporary paralysis

10. Possible Complications of Spinal Anesthesia • Hypotension • Post-dural puncture headache (“Spinal headache”) caused by leakage of spinal fluid through the puncture hole in the dura-can be treated by blood patch • “High Spinal”- can cause temporary paralysis of respiratory muscles. Patient will need ventilator support until block wears off

11. Epidural Anesthesia • Local anesthetic agent is injected through an intervertebral space into the epidural space. • May be administered as a one-time dose, or as a continuous epidural, with a catheter inserted into the epidural space to administer anesthetic drug

12. Complications of Epidural Anesthesia • Hypotension • Inadvertent dural puncture • Inadvertent injection of anesthetic into the subarachnoid space

13. IV Regional Blocks • Also known as a Bier Block • Used on surgery of the upper extremities • Patient must have an IV inserted in the operative extremity

14. IV Regional Block • After a pneumatic tourniquet is applied to extremity, Lidocaine is injected through the IV • Anesthesia lasts until the tourniquet is deflated at the end of the case

15. IV Regional Blocks • IMPORTANT- to prevent an overdose of lidocaine it is important not to deflate the tourniquet quickly at the end of the procedure • The anesthesia provider will deflate/inflate tourniquet several times before complete deflation of tourniquet cuff

16. Peripheral Nerve Blocks • Injection of local anesthetic around a peripheral nerve • Can be used for anesthesia during surgery or for post-op pain relief • Examples: ankle block for foot surgery, supraclavicular block for post-op pain control after shoulder surgery

17. Monitored Anesthesia Care (MAC) • Generally used for short, minor procedures done under local anesthesia • Anesthesia provider monitors the patient and may provide supplemental IV sedation if indicated

18. Conscious Sedation • Used for short, minor procedures • Used in the OR and outlying areas • (ER, Endo., etc) • Patient is monitored by a nurse and receives sedation sufficient to cause a depressed level of consciousness, but not enough to interfere with patient’s ability to maintain their airway

19. Inhalation Anesthetics • Nitrous Oxide- can cause expansion of other gases- use of N20 contraindicated in patients who have had medical gas instilled in their eye(s) during retinal detachment repair surgery

20. Inhalation Anesthetics • Cause cerebrovascular dilation and increased cerebral blood flow • Cause systemic vasodilation and decreased blood pressure • Post-op N&V • All inhalation anesthetics, except N20, can trigger malignant hyperthermia in susceptible patients

21. Intravenous Induction/Maintenance Agents • Propofol (Diprivan)- pain/burning on injection, can cause bizarre dreams • Pentothal (Sodium Thiopental)- can cause laryngospasm

22. General Anesthesia • During induction the room should be as quiet as possible • The circulator should be available to assist anesthesia provider during induction & emergence • Never move/reposition an intubated patient without coordinating the move with anesthesia first

23. General Anesthesia • Laryngospasm may happen in a patient having a procedure with general anesthesia • When laryngospasm occurs, it is usually during intubation or emergency • Assist anesthesia provider as needed- call for anesthesia back-up if necessary

24. Difficult Airway Cart • Anesthesia maintains a “Difficult Airway Cart” containing equipment & supplies for difficult intubations • This cart is stored in one of the anesthesia supply rooms • Page anesthesia tech if the cart is needed for your room

25. Cricoid Pressure or Sellick Maneuver • Used for patients at risk for aspiration during induction, due to a full stomach or other factors such as a history of reflux • Pressure on the cricoid cartilage compresses the esophagus against the cervical vertebrae and prevents reflux

26. Sellick Maneuver • Cricoid pressure is maintained, as directed by anesthesia provider, until the ETT cuff is inflated:

27. Regional Anesthesia • Circulator may need to assist anesthesia provider with positioning for spinal or epidural anesthesia • Patient usually is positioned laterally for placement of regional anesthesia, but may be positioned sitting upright

28. The Awake Patient • Patients undergoing surgery with regional or local anesthesia, even if sedated, may be aware of conversation and activity in room • Post sign on door to OR, “Patient is Awake” so that staff entering room will be aware that patient is conscious

29. When Patient is Awake • Limit any discussion of patient’s medical condition and prognosis • Avoid discussion of other patients & limit unnecessary conversation-- a sedated patient can easily misinterpret conversation they overhear

30. Anesthesia Monitoring Devices: • Electrocardiograph (EKG or ECG) • Pulse oximeter • Blood pressure monitor • Temperature probe • Esophageal or precordial stethoscope • End-tidalCO2Monitor

31. Malignant Hyperthermia • A rare, life-threatening complication of anesthesia • Triggered in susceptible patients by certain inhalation anesthetics (halothane, enflurane, isoflurane, sevoflurane, desflurane) and by the muscle relaxant succinycholine

32. MH • Susceptibility to MH is inherited (autosomal dominant- 50% of children of parents with MH will inherit the gene) • MH can be diagnosed by muscle biopsy-this biopsy is indicated for people who have a family history of MH

33. MH • The mortality rate from MH has been reduced from 80% to around 10% due to improvements in early recognition and treatment

34. Signs of MH • Rapid rise in body temperature (temperature may exceed 110°F)-may be a late sign • Muscle rigidity • Hypercarbia (elevated CO2) • Acidosis

35. Treatment of MH • Call for help! • Immediate discontinuation of all inhalation anesthetics • Hyperventilate with 100% oxygen • End surgery if possible • Monitor core temperature • Give only “safe” anesthetics: IV narcotics, propofol (Diprivan), nitrous oxide

36. Treatment of MH • Give Dantrolene until signs of MH are controlled • If patient is hyperthermic (core temp > 39° C or 102.2 ° F), immediately start aggressively cooling the patient: pack patient in ice, infuse chilled IV fluids, irrigate NG tube & foley catheter with ice water

37. MH Post Acute Phase • Observe patient in ICU for at least 24 hours • Continue Dantrolene for at least 24 hours

38. Dantrolene Sodium (Dantrium) • Skeletal muscle relaxant • Dantrolene is stored in the OR in the Malignant Hyperthermia Box be sure that you know where this box is located!

39. Dantrolene Reconstitution • Use only preservative-free sterile water • Add 60cc sterile water to each 20mg vial of dantrolene-shake vial until solution is clear. Dantrolene is very difficult to mix up • Initial dosage 2.5 mg/kg IV push - administer drug until symptoms of MH subside or until maximum dosage of 10mg/kg is reached • (in some cases more than 10mg/kg is needed to reverse MH)

40. For More Information… • The Malignant Hyperthermia Association of the United States (MHAUS) has a 24-hr hotline to assist medical professionals in dealing with a malignant hyperthermia crisis: 1-800-MH-HYPER (1-800-644-9737)

41. MHAUS • For non-urgent needs, information about MH can be obtained through the MHAUS organization’s web site: http://www.mhaus.org/

42. References • Gutierrez, K. (1999) Pharmacotherapeutics: Clinical Decision Making in Nursing • Malignant Hyperthermia Association of the United States (2005). Emergency therapy for malignant hyperthermia. Web site: http://www.mhaus.org/ (MHAUS hotline: 1-800-MH-HYPER) • Rothrock, J. (2002) Alexander’s Care of the Patient in Surgery